Field of the Invention
The invention relates to a device for detecting the position of a printing plate on a cylinder of a rotary printing machine.
In order to check the accurate in-register set-up of printing plates, it is generally known to use an electric circuit that is closable by the engagement of register pins of the clamping or locking bar in dimension notches on the printing plate.
For example, in the published European Patent Document EP 0 551 976 B1, there are provided electrically conductive stops for a printing plate, an electric circuit being closed by the electrically conductive printing plate when an accurate set-up or contact exists between the printing plate and the stops and, in this manner, precise positioning of the printing plate is indicated.
It is accordingly an object of the invention to provide a device for detecting a printing-plate position which operates without electrically conductive stops.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for detecting the position of a printing plate on a plate cylinder of a printing machine, comprising:
register equipment corresponding with an edge of the printing is plate, the register equipment being made up of one of stops formed of pins and bolts; and
at least one mechanical stress sensor assigned to the register equipment, the at least one stress sensor being a piezoelectric force sensor, and the at least one stress sensor being disposed one of in and in an immediate vicinity of the one of stops and bolts.
In accordance with another feature of the invention, the at least one stress sensor and the one of stops and bolts are applied to a clamping bar.
In accordance with a further feature of the invention, one of the one of stops and bolts has a circular cross section and is assigned two stress sensors.
In accordance with an added feature of the invention, the stress sensors are disposed at an angle to one another. The angle is about 30-150xc2x0, and preferably about 45xc2x0.
In accordance with an additional feature of the invention, one of the one of stops and bolts has a rectangular cross and is assigned one stress sensor.
In accordance with yet another feature of the invention, apertures and webs are formed in a region around the register equipment.
In accordance with yet a further feature of the invention, the at least one stress sensor is arranged on the webs.
In accordance with yet an added feature of the invention, the detecting device further comprises a first inductive transmitter disposed on the plate cylinder and a second inductive transmitter fixed to a machine frame. The first inductive transmitter is opposite to the second inductive transmitter for transferring data during feeding of the printing plate onto the printing cylinder.
In accordance with yet an additional feature of the invention, the detecting device further comprises at least one indicator disposed on the clamping bar.
In accordance with still another feature of the invention, the detecting device further comprises an energy source disposed on the clamping bar.
Thus, mechanical stress sensors are advantageously used as printing-plate detecting equipment.
Each piece of register equipment, which corresponds to an edge of the printing plate, has at least one mechanical stress sensor assigned thereto. The mechanical stress sensors are arranged in the region of lines of force action which are produced when a piece of register equipment experiences mechanical deformation or deflection. The mechanical stress sensors are preferably arranged in or in the vicinity of the register equipment, for example, stops, because the stresses introduced thereat are at their greatest and thus can be detected most accurately.
Particularly advantageous is an arrangement of the mechanical stress sensors in the base of the clamping bar in which the register equipment is arranged.
In an advantageous development, provision is made for weakening the region around the register equipment by forming apertures or recesses, so that the register equipment is deflected even under the action of extremely small forces. In this regard, the mechanical stress sensors can be arranged on webs which are provided between the apertures.
In an embodiment according to the invention, the mechanical stress sensors comprise piezoceramic structure-borne sound or audio sensors. Piezoceramic structure-borne sound sensors offer an advantage in that they react primarily to dynamic changes or states, such as the insertion of a plate. Slow stress changes, such as aging of the machine, distortion of mechanical components and the like are in this case not detected.
Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a device for detecting the position of a printing plate on a cylinder of a rotary printing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.